The present invention relates generally to operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a method whereby a latch profile is installed in a tubular string.
It is common practice to set a packer (or another anchoring device, such as a liner hanger or hanger/packer) in a casing string in a parent wellbore prior to drilling a branch wellbore. The packer provides a secure platform to which a whipstock may be attached during the processes of milling through the casing and drilling the branch wellbore. The packer also seals against the casing, which may be used to provide pressure isolation for a zone of the parent wellbore below the intersection with the branch wellbore, or which may aid in preventing debris from falling down in the parent wellbore.
Various types of packers have been used for this purpose—permanent packers, retrievable packers, hydraulically set packers, mechanically set packers, etc. Nevertheless, all of these various types of packers share a common disadvantage in that they restrict access and flow through the parent wellbore. If full bore access to the parent wellbore below the branch wellbore intersection is desired after the branch wellbore is drilled, the packer must be unset and retrieved from the well (which is many times quite difficult to accomplish), or the packer must be milled through or washed over (which is quite time-consuming).
Because of this wellbore restriction due to the use of packers in multilateral wellbore drilling, multilateral wells are typically constructed from bottom up. That is, a first branch wellbore is drilled from a parent wellbore, then a second branch wellbore is drilled from the parent wellbore at a location above the intersection between the parent and first branch wellbores, then a third branch wellbore is drilled from the parent wellbore at a location above the intersection between the parent and second branch wellbores, etc. This situation unnecessarily limits the options available to the operator, such as to drill the branch wellbores in another, more advantageous, sequence or to drill a previously unplanned branch wellbore below another branch wellbore, etc.
In addition, a packer relies on a gripping engagement with the casing using slips. This gripping engagement may fail due to the severe forces generated in the milling and drilling operations. Such gripping engagement also provides limited radial orientation of the packer relative to the casing, so if the gripping engagement is ever relieved (such as, by unsetting the packer), any subsequent radial orientation relative to the casing (for example, to re-enter the branch wellbore) will not be able to benefit from the original orientation of the packer.